1. Field of the Invention
The invention relates to equipment and a method for producing and/or treating a fibrous web, in particular a paper or board web.
2. Discussion of Background Information
In order to influence curl of paper webs, for example water is applied uniformly over the paper web width preferably with nozzles. It is important that the water is applied to one side or, in the event of application to both sides, is at least applied to the two sides in different quantities. The change in the swelling of the fibers between the top side and the underside of the web during the drying process is influenced in a specific manner thereby and the curl behavior is appropriately corrected.
The water can be applied via nozzles or via specific roll applicators. In particular in the case of high-quality papers, attention must additionally be paid to the best possible cross-machine moisture profile. The present invention is directed to nozzle moisteners which can be controlled section by section.
Hitherto, in each case separate devices were required for the simultaneous influencing of curl and cross-machine moisture profiles. Such known designs are, however, very costly with respect to investment and maintenance.
In the nozzle moisteners which have been usual hitherto for setting the cross-machine moisture profile, the maximum applied amount per nozzle lies in a range from 12 to 15 l/h with a droplet diameter according to Sauter≦100 μm. What is known as the Sauter diameter is an average diameter which is used for spray characterization. A drop with this diameter has the same ratio of volume to surface as the entire (spray) sample, i.e. the sum of all the surfaces and volumes.
In the case of the equipment which has been usual hitherto, the correction of the curl, i.e. the flatness of the paper, is carried out by directed to a two-row arrangement of the drying cylinders, at least at the end of the drying section, or the application of steam to the underside of the paper after the drying section and/or an additional application of water to the underside of the paper web.
With the equipment known hitherto, the result is to some extent a relatively poor flatness of the paper.